As described, Porter would be an interesting trip, and especially if you are travelling off peak (weekends for them usually) then the price is right especially for the service.
The other option would be to find the best Chicago > YYZ flight you can, then look at Westjet the rest of the way - the flight might not (won't?) be dirt cheap, but there is an upper limit to what they charge, even for the last seat in the plane.
AC will generally be competitive in price in advance (say for the first 50% of seatsd in the plance), but if the flights start to fill, their 'last seat' price is 'usually' higher.
Watch both AC and WS on Wednesdays (early!) for seat sales as well (it might be worth it for you to sign up for their weekly emails).
Have fun / Kiss the cod!
Tower, Affirmitive, gear is down and welded